Currently, in the construction of press-in type underground continuous wall (hereinafter referred to as the underground continuous wall) around the world, docking/connection between unit wall sections typically relies on mechanical socket devices to hingedly connect them one by one. At the end of construction when encircling the continuous wall, a new concrete wall unit connects with an already solidified and hardened old concrete wall unit. The mechanical sockets on the short sides of the hardened old concrete wall unit are unlikely to connect precisely with the other mechanical sockets to form a strong, continuous water-proof encircling points. The existing methods use overlapping walls on both inside and outside of the encircling seam to seal the connection to achieve waterproof and impermeability. In reality, the overlapping methods cannot achieve effective waterproof results, but also the overlapping structure is weak because it is not an integral part of the overall structure. This approach cannot meet the technical requirements for waterproof, soil retention, and weight bearing. Therefore, solving the technical problem of underground continuous wall closing without a gap is essential to ensure that the underground continuous wall will not lose its function of soil retention, water blocking, permeability resistance, and weight bearing.